Craniopharyngioma is a benign congenital tumor that occurs in the remnants of the craniopharyngeal duct during embryonic period, accounting for about 4% of intracranial tumors, and can be classified into intra-saddle type, supra-saddle type, intra-saddle-supra-saddle type and intraventricular type according to the relationship between the tumor and the saddle septum.
For supra-saddle-ventricular craniopharyngioma, the classical surgical approaches are mostly considered as transfrontal inferior approach and trans-pterygoid approach. With the development of microneurosurgical techniques, neuroimaging, neuroendoscopy, and microsurgical instruments, the supraorbital approach was first described by Jane in 1982, and the anatomical study of the supraorbital foraminal approach was reported in detail by Perneczky in 1995 [1], making supraorbital foraminal microneurosurgery a new attempt in the surgical treatment of saddle lesions.
Compared with the traditional transcranial approach, the supraorbital foramen approach adopts the lowest brow arch incision in the frontal region, which is closer to the base of the skull, allowing the evacuation of cerebrospinal fluid from the brain pool and opening up the naturally existing anatomical gaps in the skull, reducing the chance of frontal and temporal lobe strain and olfactory bundle injury.
If the tumor is only confined to the suprasellar area, the bone window can be adjusted to the medial side by using the inferior transcranial surgical route;
If the tumor grows mostly to the saddle, the incision can be extended outward selectively, and the lateral fissure can be opened to expose the second and third interstices as needed, so as to achieve the effect of miniaturized pterygoid approach, which can satisfactorily reach the saddle area and obtain the base of the frontal lobe, the medial part of the lateral fissure, the near midline area of the temporal lobe, the anterior bed process, the pterygoid crest, the orbital apex, the optic canal, the bilateral optic nerves, the internal carotid artery and its branches, the pituitary stalk, the septum and the posterior bed process. It is suitable for tumors in the saddle area, pterygoid crest, orbital apex, etc., but not for cases with large infiltrating tumors requiring skull base reconstruction.
Since the supraorbital foramen is used to display the lesions in the saddle area by the “portal mirror” effect, in order to obtain a large enough exposure of the distant lesions with a small bone window, the inner edge of the bone above the orbital rim should be removed with a grinding drill, carefully avoiding penetrating the periorbital area to ensure no obstruction in the path of the microscope beam and maximum convenience of the surgical instruments. It can be filled with bone wax and muscle to avoid postoperative cerebrospinal fluid leakage.
Adequate intracapsular resection of cystic fluid, calcified material and substantial part of the tumor is performed first, in order to further obtain the largest resection gap between the tumor and optic nerve and optic cross, and to reduce the strain on nerves and blood vessels, which is an important aspect affecting the total resection of the tumor.
The supraorbital locking hole is used to resect larger saddle lesions with small bone windows, which has a small operating space and high technical requirements, therefore, how to improve the total resection rate within the limited surgical space is the key.
Most scholars believe that there is a glial proliferation layer between the craniopharyngioma and normal neural tissue, and the tumor is separated from this level during surgery, and structures such as pituitary stalk, funnel, medial bulge and gray nodes that are closely adhered to the tumor are identified under high magnification and carefully separated, so that total resection of the tumor can be achieved without damaging the normal structures; partial resection of the tumor may recur after surgery, and the recurrent tumor adheres to the surrounding structures, giving The partial resection of tumor may recur after surgery, and the recurrent tumor may adhere to the surrounding structures, causing difficulties and dangers to the second surgery. Therefore, it is advocated that the first surgery should actively achieve total resection of the tumor.
However, the tumor is often not fully resected during surgery due to close adhesions with hypothalamic structures, poor intraoperative tumor exposure, large calcifications, and close adhesions between the tumor and penetrating arteries and great vessels. For craniopharyngioma with tumor diameter > 4 cm, it is difficult to completely resect the tumor because of the adhesion of the tumor parenchyma and calcification to the lower part of the optic thalamus, and the limitation of the transcranial view, the posterior part of the tumor is easy to remain;
In addition, the presence and degree of tumor calcification are also factors that affect total resection and lead to postoperative recurrence. In addition, the presence and degree of tumor calcification is also a factor that affects total resection and causes recurrence after surgery. Large hard tumor calcified plaques often adhere closely to the visual cross, the base of the three ventricles, the hypothalamus, the internal carotid artery and its branch vessels, the superior wall of the cavernous sinus, the saddle diaphragm and other structures, and occupy valuable space for surgical operation, making intraoperative separation extremely difficult, and forcible removal may cause damage to the above structures. The sharp separation may damage the blood vessels supplying the lower part of the optic thalamus and other important structures, which makes the total resection difficult.
On the contrary, cystic tumor is a favorable factor for total surgical resection. In completely cystic tumor, since there is no calcified spots and other substantial tumor components closely adhering to the surrounding structures, the tumor can often be peeled off completely along the cystic wall, and the decompression of the cystic cavity also provides enough operating space for surgical operation.
Severe dysuria and electrolyte disturbances are often seen after craniopharyngioma surgery, so protection of the pituitary stalk has always been important to the surgeon. Since craniopharyngiomas originate from different parts of the pituitary stalk, the tumor is closely related to the pituitary stalk, and the traction and separation of the tumor during surgery will inevitably affect the hypothalamic function, and the postoperative endocrine changes are less severe in cases where the pituitary stalk is identified and protected intraoperatively than in cases where it is not identified or unidentified. Therefore, understanding and identifying the common location of the pituitary stalk during craniopharyngioma surgery can help to identify and protect the pituitary stalk early intraoperatively and reduce the damage to the hypothalamus.
It has been found that the pituitary stalk is most often located posteriorly and inferiorly to the tumor (including laterally and posteriorly), followed by superiorly and laterally to the tumor, and rarely anteriorly to the tumor. Due to the growth and compression of the tumor, the pituitary stalk is displaced, twisted and elongated and thinned, sometimes it is difficult to identify it intraoperatively, but the pituitary stalk can be found mostly from the medial bulge of the funnel and the foramen of the saddle diaphragm, and the vein medullary lines on the surface of the longitudinal pituitary stalk can be seen, which is beneficial to the judgment; even if the pituitary stalk is broken during the intraoperative separation of the tumor, the tumor should be carefully separated from the pituitary stalk and the residual pituitary stalk should be kept intact, which is beneficial to the postoperative hypothalamic function. This will facilitate the recovery of hypothalamic function after surgery.
The arteries supplying the craniopharyngioma come from the penetrating arteries of each segment of Willis ring, among which the intersaddle part receives blood from the branches of the internal carotid artery in both sides of the cavernous sinus, the extraaddle part receives blood from the small branches of the anterior communicating artery and the adjacent anterior cerebral artery in the front, and the branches of the posterior communicating artery in the side. The posterior communicating artery, anterior choroidal artery, thalamic perforator artery and arteriolar nerve in the lateral interstitial space of internal carotid artery are mostly attached to the surface of the tumor, so careful identification is needed to prevent damage.
The tumor should be resected intratumorally as far as possible, and the tumor should be loosened before pulling and turning the tumor wall in a small extent, and the action should be gentle so as not to tear the new tumor-supplying vessels emanating from the internal carotid artery, etc. The tiny tumor-supplying vessels limited to the surface of the tumor should be cut off by electrocoagulation under the operating microscope.
In one of the cases in this group, the adhesion of the electrocoagulation forceps tore the new small vessels supplying the tumor in the internal carotid artery and caused hemorrhage.
In addition, special attention should be paid to protect the penetrating arteries and collateral branches from the internal carotid artery, the posterior communicating artery, the anterior choroidal artery and the posterior cerebral artery to the hypothalamus and the anterior perforating mass; when removing the posterior superior tumor, special attention should be paid to prevent damage to the posterior thalamic arteries and the basilar artery that supply the posterior perforating mass and the interpeduncular fossa, which are closely related to the functions of the midbrain reticular formation, the pyramidal tract and the spinal thalamic tract. Penetrating arteries, intraoperative injury to these arteries or excessive stretching and prolonged exposure are prone to vasospasm, which will cause ischemia in a large area of the shell nucleus and internal capsule and thalamus.
In addition to the short operative time, rapid postoperative recovery, and aesthetic incision, the most important point is that the supraorbital foraminal approach is only a miniaturization of the approach, which reduces the damage to soft tissues and skull, but in no way means that it necessarily reduces the trauma to brain tissue and the risk of neurological impairment. Therefore, extremely strict requirements are placed on the surgeon’s skillful microsurgery skills, extensive surgical experience, knowledge of microscopic neuroanatomy, extremely patient and dedicated surgical style, and sound preoperative planning.
The emphasis is never only on the size of the craniotomy window itself, but on the careful design of each lesion, determining the exact location of the craniotomy, reaching the lesion area with minimal damage to the surrounding tissues, and removing the tumor as completely as possible; otherwise, it will be counterproductive.